The answer to 'why is my mini split not working' is that there can be several common causes, such as a refrigerant leak, a faulty compressor, electrical issues, or a clogged air filter. Symptoms may include the unit not powering on, poor cooling/heating performance, or strange noises.
If your mini split is not working properly, the first step is to check the air filter and clean or replace it if needed. You can also inspect the outdoor unit for any visible damage or leaks. However, more complex issues like refrigerant leaks or compressor problems will likely require a professional HVAC technician to diagnose and repair.